The present invention relates to an apparatus for optical monitoring of whether a thread or weft is in motion or not in a region illuminated by one or more light sources.
Prior art contact-free signal emitters of the optical type permit substantially only sensing of the presence of and/or slight and/or slow movements of a thread or a weft. In many cases, it is desirable to establish not only whether a thread or weft is located at a given position but moreover whether the thread or the weft is in motion in a determined direction at the desired location. Prior art optical signal emitters do not carry this feature and particularly not so if the thread is extremely thin and/or has a smooth or shiny surface.